The device of the instant invention was developed to solve a problem currently confronting over 60 atomic power plants around the world. These plants were built by General Electric and incorporate a large volume of water surrounding the reactor itself. This water is contained within a large thermos bottle-shaped vessel having a wall consisting of a four and five-sixteenths inch thickness of carbon steel clad with an inner lining of one-fourth inch stainless steel. That wall is surrounded by a concrete revetment spaced therefrom a distance of forty inches. The water pipes supplying this reservoir are also lined with stainless steel, and pass horizontally through the steel wall. They terminate at the innermost surface of the vessel, where their circular intersection with the wall was initially hand ground to a slightly rounded edge.
The areas of circular intersection between the pipes and the inner surface of the vessel have developed cracks after prolonged use. Those cracks pose serious questions of safety and must be repaired. The cracked material must be removed to prevent further penetration of the cracks into the vessel.
Removal of the damaged material is complicated by radioactive conditions around the vessel. It must be accomplished from outside the inner wall because a person cannot safely enter the vessel to set up or operate a boring or milling machine. The closest access available is through the pipe itself from the forty-inch wide area between the wall and the revetment. For this, the pipe must be cut and the water sealed out. It should be noted here that an individual worker can be exposed to the radiation in this area for only a short time. Therefore, any tool used must be quickly set up and operated remotely.
Conventional boring tools are not sufficiently portable or versatile for this job. They are not only very bulky and complicated to assemble, but also lack sufficient remote adjustment capabilities to make the cuts required here. This adjustability is important in performing both the boring and facing operations.